java Java中的倒直三角形
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Upside down right triangle in Java
提问by John
I need to do this:
我需要这样做：
*****
****
***
**
*
and I have this code:
我有这个代码：
for (int i=0; i<5; i++)
{
for (int j=5; j>i; j--)
{
System.out.print("*");
}
System.out.println("");
which outputs this:
输出这个：
*****
****
***
**
*
I cant figure out how to implement the spaces. Any help appreciated.
我不知道如何实现空间。任何帮助表示赞赏。
回答by Tunaki
You need to use two for-loops: one for the number of spaces and one for the number of *:
您需要使用两个 for 循环：一个用于空格数，另一个用于*：
for (int i = 0; i < 5; i++) {
for (int j = 0; j < i; j++) {
System.out.print(" ");
}
for (int j = i; j < 5; j++) {
System.out.print("*");
}
System.out.println();
}
Java 8 solution:
Java 8 解决方案：
IntStream.range(0, 5).forEach(i -> {
IntStream.range(0, i).forEach(j -> System.out.print(" "));
IntStream.range(i, 5).forEach(j -> System.out.print("*"));
System.out.println();
});
回答by Wander Nauta
Here's a solution with one less loop than the other answers, if you really want to wow the person who's grading your assignment:
这是一个比其他答案少一个循环的解决方案，如果你真的想让给你的作业评分的人惊叹：
for (int y = 0; y < 5; y++) {
for (int x = 0; x < 5; x++) {
System.out.print((x >= y) ? "*" : " ");
}
System.out.println();
}
回答by user3437460
Just print knumber of spaces before start of every line.
只需k在每行开始之前打印空格数。
To solve this kind of problems, it will be easy if you break it down and observe the pattern.
要解决这类问题，分解并观察模式会很容易。
***** 0 space
**** 1 space
*** 2 spaces
** 3 spaces
* 4 spaces
After taking note of this pattern, you ask yourself will you be able to print this?
记下这个图案后，你问自己你能打印这个吗？
0*****
1****
2***
3**
4*
We see that the number is similar to the start of every line. Hence we could make use of variable i. (your outer loop counter) and we have..
我们看到数字与每一行的开头相似。因此我们可以使用变量 i。（你的外循环计数器），我们有..
for (int i=0; i<5; i++){
System.out.println(i);
for (int j=5; j>i; j--){
System.out.print("*");
}
System.out.println("");
}
Now, you just have to convert your numbers at the start of every line to the number of spaces and you have..
现在，您只需将每一行开头的数字转换为空格数，您就可以......
for (int i=0; i<5; i++){
for(int k=0; k<i; k++) //using i to control number of spaces
System.out.println(" ");
for (int j=5; j>i; j--){
System.out.print("*");
}
System.out.println("");
}
